This invention relates to spiral displacement machines in which a displacer having spiral vanes is driven eccentrically in a housing having spiral vanes.
Spiral displacement machines, which are also called spiral superchargers or volute superchargers, are disclosed in MTZ Motortechnische Zeitschrift 46 (1985) at pages 323-327. They are used especially for supercharging internal combustion engines. For this purpose, a displacer which revolves eccentrically is mounted in a housing. Both the housing and the displacer have spiral vanes which interact with one another periodically and together form working chambers which rotate spirally in the housing. To obtain the highest possible efficiency, both the outer and inner surfaces of the vanes of each of the two parts, i.e., the housing and the displacer, are used periodically to form a working chamber with the inner or outer surface of the other of the two parts, i.e., the displacer or the housing. In addition, the number of working chambers is doubled by providing two spiral vanes symmetrically arranged about the axis of the displacer. To avoid having spiral vanes which extend a long distance in the axial direction from a supporting disk, the displacer consists of a central disk with spiral vanes extending axially from both sides of the disk. In this way, a total of eight working chambers is obtained, and when the vane arrangement is completely symmetrical, as described in the above-cited MTZ publication, all of the working chambers open and close simultaneously. The resulting pressure variation, particularly at the outlet of the spiral displacement machine, produces a high noise level, which requires effective acoustic insulation.